1. Field of the Invention
The present invention relates to a surveying instrument which measures a distance and an angle to a measured object by tracking a reflector provided at the measured object, and in particular, relates to a surveying instrument which can shorten a search time of the measured object.
2. Description of the Related Art
In the past, surveying work was carried out by using a surveying instrument provided at a control point, and by using a reflector (corner cube, etc.) of a measured object in which a surveying instrument collimates (setting of the optical axis of the telescope in the direction of the measured object). The surveying instrument has a horizontal-angle-measuring unit and a vertical-angle-measuring unit which detect a collimating direction, and a laser rangefinder that measures a distance from the surveying instrument to a collimated target. In recent years, the surveying instrument has an auto-tracking function for tracking the reflector automatically (collimated target) of the measured object, so a surveyor can take measurements alone.
In such a surveying instrument, a surveyor exists in the collimated target side, and moves the collimated target according to a work schedule. When the surveyor moves the collimated target, the surveying instrument tracks the collimated target and collimates the collimated target automatically.
The auto-tracking function of the surveying instrument is achieved by a driving section for driving a tracking-light-emitting section around a horizontal axis and a vertical axis, a tracking-light-emitting section for emitting a parallel tracking light to the reflector of the collimated target, and a tracking-light-receiving section for receiving a tracking light reflected by the reflector. When the driving section is controlled and a tracking light is located at the center of a light-detecting element in the tracking-light-receiving section, the surveying instrument can track the collimated target.
A trackable range is limited to a collimating range of a telescope section of the surveying instrument. Therefore, when the move speed of the collimated target moved by the surveyor is faster than the trackable speed of the surveying instrument, or when the collimated target is outside in the collimatable range, the surveying instrument loses sight of the collimated target and cannot track it. In this case, the surveying instrument searches the collimated target by rotating around a horizontal axis and a vertical axis. For example, Japanese Unexamined Patent Application Publication No. 2000-356518 discloses an invention relating to such a surveying instrument.
Furthermore, for example, Japanese Unexamined Patent Application Publication No. 8-178652 discloses the following invention. In this invention, a surveying instrument and a measured object receive positional information by GPS receiver, and the surveying instrument receives position information of the measured object by wireless, and then the surveying instrument searches a collimated target by position information of itself and position information of the measured object.